This Week's Doctor Who Is Must-Watch Sci-Fi

It doesn't matter if you're a fan of Doctor Who or not: this week's episode, "Flatline," is just plain good sci-fi. After a season with a lot of material that's felt like a retread of showrunner Steven Moffat's greatest hits, it's great to land on an episode that takes us somewhere that feels completely new. The star of the episode is an all-new monster with some thoroughly unique -- and thoroughly creepy -- visuals. (Really, the art department deserves some major kudos for bringing the episode's unusual concept to life.)

But the monster of the week, no matter how unique, can't push aside great moments with both The Doctor and Clara, with Clara forced to take on the role of The Doctor after he's trapped in the TARDIS. The resulting episode has great visuals, more than a few laughs, and some real chills, and Peter Capaldi finally getting a proper "Doctor" speech, which the series somehow hasn't gotten around to giving him yet.

So if you haven't watched it yet... what are you still doing here? "Flatline" is a must-see for fans. You can see new episodes of Doctor Who on Saturday nights on BBC America -- though cord-cutters will have to pick up the current season on iTunes or Amazon Instant. If you want to catch up on earlier seasons, they can be found on both Netflix and Hulu.

The Doctor and Clara going on a farewell trip for one last hurrah before she leaves for good. It's a trip on the Orient Express, which is a space train.

The trip quickly turns into an adventure as people on the train start dying, picked off by the mythical creature The Foretold. (What is it with this show and the definite article?)

The Doctor displayed his now-trademark disregard for the deaths of others, focusing instead on solving the week's mystery... but when he does save someone after telling Clara there was no hope, she asks if he only pretends to be heartless.

Though Clara (and the audience) don't get a firm answer on that question, the suggestion that The Doctor still is doing his best to save people even when he doesn't always manage is enough to convince Clara to keep traveling with him.